Mode of action
To access a detailed description and calculations please refer to the scientic publication from "Lehrstuhl fuer Energiesysteme" at Technical University Munich :
The usabilty of the Misselhorn-process, its advantages and high effiency at low temperature levels is based on the following:
The Misselhorn-process uses - similar to the known ORC process - an organic fluid as a working medium. The vaporisation of the working fluid takes place in a batch mode in several, minimum 3, typically 6, heat exchangers, which are arranged in parallel. These are cycling through different timed phases, which are realised by a cyclical, simultaneous switching of the mass flows of both the working fluid as well as the heat source. Batch mode vaporisation on this note means a isochore vaporisation in a closed pressure vessel, while heat is constantly supplied.
At each specific time one heat exchanger(the one with the lowest temperature level) is being filled with working fluid, while in the other heat exchangers (except the one with the highest temperature level) the still largely fluid working medium is locked in, while heat is constantly supplied. During the next cycles the batch vaporisation continues until the highest possible temperature level and the highest possible pressure level of the working medium is achieved. After expansion of the working medium from the heat exchanger with the highest temperature and pressure level through the expansion engine, this heat exchanger is being filled in the next cycle with fluid, undercooled working medium. With this, the cycle "filling - batch vaporasation - expansion" starts again.
At the same time the heat source flows through the heat exchangers in a serial way, whereas the heat source first flows through the heat exchanger with the highest temperature of the working fluid, and last flows through the heat exchanger with the lowest temperature of the working fluid. The temperature difference between the heat source and the working fluid is idaelly adapted in each heat exchanger, hence there is is no "pinch point" limitation as with an ORC process.
The highest possible pressure level is detemined by the maxmimum temperature of the heat source. The usable time slots for exchanging heat from the heat source to the working fluid are increased to an extent, that the process is suitable for low temperatures of the heat source. Additionally, the need for auxiliary energy is reduced because the workuing fluid is only transported instead of being pressurized. Instead of a turbine a modified piston engine is being used. The heat exchangers can be implemented with standard plate heat exchanger products; a number of 6 heat exchangers (plus one condenser) will achieve the described efficiency advantages in the best econmic way.
Waste heat as primary resource for the Misselhorn process is available virtually for free as it is abundant and renewable! The profitability calculation for the MWM system is dependent on the amount of generated electricity in kWh (and the monetary value of it) and the cost of acquisition, installation and maintenance. According to the individual circumstances the MWM system amortises within 3 to 6 years.
Several patents for the Misselhorn technology have been applied or already granted:
it is about: